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Add new transformation: // (~A | ~B) == (~(A & B)) 

llvm-svn: 5738
This commit is contained in:
Chris Lattner 2003-03-10 23:13:59 +00:00
parent f7a838595c
commit 3e327a4334
1 changed files with 19 additions and 8 deletions
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27
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -446,6 +446,7 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
Op1NotVal,I.getName()+".demorgan",
&I);
WorkList.push_back(Or);
return BinaryOperator::createNot(Or);
}
@ -470,15 +471,25 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
if (RHS->isAllOnesValue())
return ReplaceInstUsesWith(I, Op1);
if (Value *X = dyn_castNotVal(Op0)) // ~A | A == -1
if (X == Op1)
return ReplaceInstUsesWith(I,
ConstantIntegral::getAllOnesValue(I.getType()));
Value *Op0NotVal = dyn_castNotVal(Op0);
Value *Op1NotVal = dyn_castNotVal(Op1);
if (Value *X = dyn_castNotVal(Op1)) // A | ~A == -1
if (X == Op0)
return ReplaceInstUsesWith(I,
ConstantIntegral::getAllOnesValue(I.getType()));
if (Op1 == Op0NotVal) // ~A | A == -1
return ReplaceInstUsesWith(I,
ConstantIntegral::getAllOnesValue(I.getType()));
if (Op0 == Op1NotVal) // A | ~A == -1
return ReplaceInstUsesWith(I,
ConstantIntegral::getAllOnesValue(I.getType()));
// (~A | ~B) == (~(A & B)) - Demorgan's Law
if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
Op1NotVal,I.getName()+".demorgan",
&I);
WorkList.push_back(And);
return BinaryOperator::createNot(And);
}
return Changed ? &I : 0;
}